A single slit of width 4.90 μm was formed by chemically etching a 0.17 μm thick chromium film deposited on glass. The diffraction pattern obtained when the slit was illuminated with light from a 10 mW He–Ne laser, polarized first parallel and then perpendicular to the slit, was experimentally determined for angles of incidence between 0° and 45°. The measured diffraction patterns were first compared with predictions made using the scalar Helmholtz equation with either the Kirchhoff or the Rayleigh–Sommerfeld obliquity factors. The experimental patterns were also compared with the results of an exact numerical solution of Maxwell’s equations for the diffraction problem using the method of Neerhoff and Mur. All theoretical predictions agreed well with measurement for incident angles smaller than 10°, and, although no prediction agreed exactly with measurement at the largest angles of incidence, predictions obtained using the scalar Helmholtz equation with the Kirchhoff obliquity factor agreed with experiment best overall.

Topics
Maxwell equations, Partial differential equations, Fraunhofer diffraction, Geometrical optics, Optical properties, Lasers, Transition metals
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© 1994 American Association of Physics Teachers.
1994
American Association of Physics Teachers
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